This project will study the sequence of events in the lung induced by cigarette smoking which culminates in emphysema. Our working hypothesis is that the induction of emphysema, which develops in certain cigarette smokers, depends upon alteration of the protease:protease inhibitor balance through an increase in extracellular elastase, which may be exacerbated by stress on the oxidant:antioxidant balance in the lung. Smoke exposure causes the formation of a stable chemoattractant which stimulates neutrophil influx into the lung parenchyma. Neutrophils release elastase during migration from the circulation into the airspaces. Both of these events occur in the canine model of cigarette smoke exposure. The first specific aim is to analyze the regulation of the process of in vivo elastase delivery into the lung by: (a) examining the nature and cell-specificity of the cigarette smoke-induced chemoattractant; (b) characterizing the in vivo and in vitro degranulation response of the neutrophils by elastase quantitation and immunolocalization; and (c) evaluating the effect of pharmacologic agents on smoke-induced neutrophil influx and elastase release. The second specific aim is to determine the response of the lung's antioxidant defense screen to acute and chronic cigarette smoke exposure by measuring: (a) thiol levels and activities of enzymes that maintain reduced glutathione levels; (b) activities of enzymes that remove reactive oxygen species; and (c) changes in levels, distribution and localization of methionine sulfoxide peptide reductase in the lung. The protease:protease inhibitor balance may be altered by smoke-induced oxidative inactivation of alpha-1-protease inhibitor, the primary protease inhibitor in the lung. The antioxidant defense screen may prevent inactivation of alpha-1-protease inhibitor or restore function to inactivated inhibitor; however, cigarette smoke may also alter the reductive capacity of the lung. In addition, the inhibitor may be overwhelmed locally by increased availability of neutrophil elastase. These studies will provide insight into the interaction of the protease:protease inhibitor balance with the lung antioxidant defense screen.